How To Send Direct Message Via Firebase From User To User?

I am really rookie and need an advice. I have read documentation, and as far as i understood if you need send direct message, follow next steps: Make authentification, eventually

Solution 1:

Your suggested approach sounds good. The most important thing to realize is that you require an app server to send a downstream message to a device. Using the database as the communication mechanism between the app and the app server is a popular approach.

You could also use Cloud Messaging's upstream capabilities. But I've never tried that approach, because the database works fine for me and I had little interest in learning yet another protocol (XMPP).

You can read how I implemented it in this Firebase blog post Sending notifications between Android devices with Firebase Database and Cloud Messaging.